A submarine has gone missing in Indonesia. The country’s navy said it went missing in north Bali and 53 people are on board.

It was carrying 49 crew members, its commander, and three gunners.

Indonesia’s navy is currently searching for it. Military chief Hadi Tjahjanto said the navy has deployed scores of ships to search the area, including a hydrographic survey ship, and has asked for help from Singapore and Australia, which have submarine rescue vessels.

Tjahjanto said the KRI Nanggala 402 was participating in a training exercise when it missed a scheduled reporting call.

The submarine is believed to have disappeared in waters about 60 miles (95 kilometers) north of Bali, he said.

Local media reports said the navy believes the submarine sank into a trough at a depth of 700 meters (2,300 feet).

The Defense Ministry said in a statement that the submarine lost contact after being granted clearance to dive. It said a helicopter later spotted an oil spill near the dive’s starting position.

The German-built submarine, which has been in service in Indonesia since 1981, was rehearsing for a missile-firing exercise that was to take place on Thursday. Tjahjanto and other military leaders were to attend.

Indonesia currently has a fleet of five submarines and plans to operate at least eight by 2024.